POU transcription factors have been shown to be important in the regulation of cell fate decisions during development. We have focused on understanding the function of one POU domain gene, XlPOU 2 , in early neural development. To generate "knockout" of function in Xenopus, a construct consisting of the engrailed repressor or VP16 activator was fused to the POU domain of XlPOU 2. This construct will be under the regulation of the dexamethasone and will be injected into the A1 lineage, a lineage that will become the future brain. Thus, both temporal and spatial expression of the "dominant-negative" construct should enable us to assess the function of XlPOU 2 in early neurogenesis. In order to understand the cascade of events that follow neural induction, a subtraction scheme to clone genes that up-regulated or down-regulated by the neural induction factor, noggin is underway. Several novel candidate genes have been identified and are being characterized. We have also cloned and characterized a novel Brain-1-related POU gene in zebrafish, tai-ji. Taiji is a hallmark of proliferating, non-differentiated cells of the adult teleost nervous system. The characterization of human and mouse tai-ji and its role in neural stem cells will be examined using primary progenitor cultures of neurons and gene ablation in the mouse.